New Guinea is the world’s largest, most speciose, and most culturally rich tropical island, and the little-studied Mamberamo Basin of Papua (Indonesian New Guinea) is recognised among the region’s most-important areas for biological diversity. Here, we examined the floodplain forests in the indigenous territory of Papasena, within the Mamberamo-Foja Wildlife Reserve in the Mamberamo Basin. As part of a training activity with local researchers, students, and civil servants, and with the permission and assistance of the local people, we employed various methods including the field surveys detailed here. We used variable-area tree plots, transects for non-trees and soil sampling, and local informants to document 17 plots: four in old-growth dryland forest, five in old-growth swamp forests (two seasonally flooded and three permanently wet including one dominated by sago, Metroxylon sagu Rottb.), five in secondary forest (fallows), and three in gardens (two in swamps and one on dryland). In total, we measured 475 trees over 10 cm in diameter at 1.3 m (dbh). The swamp forests had high local basal areas (highest value 45.1 m2 ha−1) but relatively low statures (20 m but with emergent trees over 40 m). In total, 422 morphospecies from 247 genera and 89 different families were distinguished. These included 138 tree species and 284 non-tree plant species. A quarter (105) of the morphospecies lacked species-level identifications. The woody families Rubiaceae, Araceae, Moraceae, and Euphorbiaceae were especially diverse, with 20 or more morphospecies each. Tree richness was highest in dryland forest (plot 7 having 28 species in 40 stems over 10 cm dbh) with more variation in the flooded forests. Non-tree vegetation showed similar patterns ranging from 65 species in one 40-by-5 m primary forest plot to just 5 in one seasonally flooded forest plot. The local people identified many plants as useful. Among trees, at least 59 species were useful for construction (the most common use), while, for non-trees, medicinal uses were most frequent. Inceptisols dominated (12 plots), followed by Ultisols and Entisols (3 and 2 plots, respectively). Drainage appeared poor and nutrient availability low, while land-suitability criteria implied little potential for crops aside from sago. We discuss the implication of local practises and more recent developments that may threaten the conservation of these floodplain systems. We underline the key role of local people in the oversight and protection of these ecosystems.
Tag: floodplains
Agricultural intensification is causing rapid habitat change in the Tonle Sap Floodplain, Cambodia
The Tonle Sap Lake and Floodplain (TSLF) supports many globally threatened species and its fishery has sustained Cambodia’s people for millennia. The rate of habitat loss has accelerated in recent years due to political and economic conditions, and a warming climate and El Niño events that created opportunities for people to burn scrubland at an elevated rate. Here, we use a point-based landcover assessment method to document the impacts of local-scale drivers, in particular agricultural intensification, on habitat trends between 1993 and 2018. The areal extent of scrubland and grassland in the TSLF declined from ~ 74% in 1993 to ~ 52% in 2018, as a result of intensification and expansion of rice cultivation. During that time period, grassland cover declined from ~ 3160 to ~ 519 km2, whilst between 2008 and 2018, scrubland cover declined from ~ 8660 to ~ 6776 km2. Habitat loss has had catastrophic implications for grassland-dependant species, such as Bengal Florican, and, we estimate that habitat changes in the TSLF may have caused carbon stocks to decline by 12% while fish productivity is also likely to have dropped, with significant implications for food security. To put this habitat loss in context, losses over the past 10 years have been nearly twice as large as published predictions of the amount likely to be lost between 2010 and 2040 due to hydropower. We suggest that the expansion and intensification of rice cultivation is the greatest current threat to habitats in the TSLF and deserves greater attention from policy makers and practitioners.